The proposed project involves an investigation of the ability of macrocyclic polythiaethers to complex and mobilize heavy-metal ions in biological systems. Kinetic and thermodynamic studies, in vitro, will examine the effects of ring size and structure upon both the formation and dissociation rate constants for these ligands reacting with copper(II) and mercury(II) ions as a means of generating information relevant to selective ion-transport phenomena. Correlated animal studies will be conducted with selected ligands to establish their effectiveness as purging agents for heavy metal ions, specifically mercury(II).